Mitochondrial DNA vs Nuclear DNA
Deoxyribonucleic acid (DNA) is the main heredity material in almost all the organisms except some viruses. It is considered as a biological macromolecule, consisting of two long polymer strands made up of small repeating monomers called nucleotides. These complementary strands are twisted along a common axis, to form the unique structure of DNA known as ‘double helix’ structure. Almost all the human cells have DNA, except red blood cells and nerve cells. Depending on the residing place, there are two types of DNA present in a cell; nuclear DNA and mitochondrial DNA.
What is Nuclear DNA?
Nuclear DNA is found in the nucleus in a cell and is important to store information for maintenance of cell functions and growth. There are two copies of nuclear DNA per each cell that come from both parents. Therefore, nuclear DNA is both maternally and paternally inherited. These DNAs are unique to individuals except identical twins.
What is Mitochondrial DNA?
Mitochondria is an organelle found in all eukaryotic cells and that functions in converting chemical energy into useful energy sources in cells. Unlike most other organelles, mitochondrion has its own non-nuclear complement of DNA, known as mitochondrial DNA or mtDNA. Each mitochondrion has between two to ten copies of a circular DNA. Each mitochondrial DNA is specific to carry out a particular set of functions associated with mitochondria, including the synthesis of molecules that are used for cellular respiration, units that code for the synthesis of tRNA of each amino acid, and DNA involved in the synthesis of rRNA that uses for protein synthesis.
The uniqueness of mitochondrial DNA is that it is maternally inherited as a linked set of genes, passed on to progeny in the cytoplasm of the egg cell; thus no recombination between maternal and paternal genomes occurs.
What is the difference between Mitochondrial DNA (mtDNA) and Nuclear DNA?
• Mitochondrial DNA is found inside the mitochondria while nuclear DNA is found inside the nucleus of a cell.
• One cell contains approximately 99.75% of nuclear DNA and 0.25% of mitochondrial DNA.
• The mutation rate of mitochondrial DNA is nearly twenty times faster than that of nuclear DNA.
• Mitochondrial DNA is circular in shape while nuclear DNA is linear in shape.
• Mitochondrial DNA is smaller than nuclear DNA.
• Each mitochondrion contains thousands of mitochondrial DNA copies, but only a few copies of nuclear DNA exist in a human cell nucleus.
• Unlike nuclear DNA, all mitochondrial DNA comes from the mother and none comes from the father (maternally inherited). Nuclear DNA contains more information coming from both parents (both paternal and maternal).
• Unlike nuclear DNA, mitochondrial DNA can only be used to determine maternal lineage in an individual or a group, and it cannot be used to determine paternal lineage.
• Mitochondrial DNA may not be closely correlated to an individual’s fitness from other populations as nuclear DNA.
• Mitochondrial DNA is found within the matrix of the organelle. Therefore, unlike nuclear DNA, it is not enclosed within a membrane.
• Mitochondrial DNA may contain more than thousand copies per cell while nuclear DNA has only two copies per cell.
• The chromosomal paring of nuclear DNA is diploid whereas that of mitochondrial DNA is haploid.
• Generational recombination and replication repair is present in nuclear DNA. In contrast, these processes are absent in mitochondrial DNA.
• Reference sequence of nuclear DNA has been described by the ‘Human Genome Project’ in 2001 while that of mitochondrial DNA has been described by ‘Anderson and co-workers’ in 1981.
• When considering the size of genome, nuclear DNA consists of about 3.2 billion bp (base pairs) and mitochondrial DNA consists of about 16,569 bp.